Some legends date missionary activity in the northern coast of the Black Sea back to the apostolic era, while some hagiographical sources trace it to the period of Diocletian and Constantine I. In the 6th century, these missions were connected with the empire’s political activity, while during the Iconoclasm missionary activity passed into the hands of the exiled Iconophiles. The missionary activity of Constantine (Cyril) concerned also the Pontic region. Part of the Tatars of Crimea was converted in the Palaeologan era.